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New Methods for Evaluating the Appropriateness of Solar Simulators

Given by: Dr. Robert Sayre
Rapid Precision Testing Laboratories

Wednesday, February 20, 2008

4:00pm in Manning Hall room 201

Refreshments will be served at 3:30pm in Manning Hall room 222


Submitted to the FDA in December 2007

Docket: 1978N-0038 - Sunscreen Drug Products for Over-the-Counter Human Use; Proposed Amendment of Final Monograph. Comment on UVA Solar Simulator for Sunscreen Testing. The currently proposed solar simulator for UVA sunscreen testing has been described as having too little UVA-1. The proposed FDA standard will perpetuate this problem causing the UVA protection of sunscreen products to be over estimated and thereby misrepresent sunscreen products actual protection in sunlight.

Representative UVA solar simulators meeting the proposed FDA standard at either end of the proposed spectral limit will produce UVA protection values from twice to three times greater than the UVA protection actually provided against natural sunlight.We propose that the UVA spectral region (320-400 nm) of the CIE Air Mass 1.0 solar reference spectrum be adopted as the FDA standard for UVA solar simulators.

Goodness of Fit Indices for the persistent pigment darkening (PPD) effectiveness of sunlight at different solar zenith angles ranges from ~93% -100% relative to the standard CIE Air Mass 1 solar spectrum. The current UVA filtered solar simulators have PPD Goodness of Fit Indices of less than 80%. We propose that solar simulators for UVA sunscreen testing would be deemed to comply with the standard if their PPD effective Goodness of Fit Index exceeded 90%.

We have determined that a xenon arc source filtered with a simple idealized dichroic band pass filter, passing a band of UVA from 320 to 400 nm and blocking visible and shorter UV outside this band, produces a UVA solar simulator with a Goodness of Fit Index for PPD effective irradiance of ~94%. Comparison of our proposed UVA solar simulators cumulative effective spectrum to those of CIE Air Mass 1.0, 1.5 & 2.0 solar spectra shows that throughout a broad range of solar angles the UVA spectral effectiveness distribution is comparable.

This means that the PFA for a sunscreen product in a laboratory clinical test will be predictive of UVA protection afforded consumers, using the sunscreen product as prescribed, outdoors under normally varying solar angle sunlight. This clearly suggests that the human laboratory clinical test does not need to be compared to an investigatory in vitro test which does not apply the product to individual volunteers and test there response to exposure.

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